While that prison is built on a similar, circular design, it is not the same as it has hallways and the cells are at 90 degrees to the center.

The horror of the true Panopticon is that the cells have no doors, just metal fences, and they all face into the center where the guard tower is located. The prisoners are under direct observation at all times, and never know when they are being observed.

The closest to a "true" Panopticon may be the old Joliet prison in Illinois:

It still had doors, though, so you could sit down with your back against the door and not be visible.